Rate-determining collapse of a tetrahedral intermediate in ester aminolyses in aprotic solvents

Menger, Fredric M.; Smith, Jerry H.

doi:10.1016/s0040-4039(01)98693-9

Cited by 14 publications

(11 citation statements)

References 13 publications

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“…The activation energy, enthalpy, and entropy of the process were determined. Correlations of the N-acylation rate constants of the a-amino acids with the composition of the binary solvent at various temperatures were established, and the N-acylation rate constants of the a-amino acids in water were determined.Kinetics of ammonolysis of esters in nonaqueous media have been studied in [1,2]. There have been a number of works devoted to the effect of the structure of the RCO radical in ROX on the reactions of phenyl esters and derivatives of aliphatic carboxylic acids with various amines in dioxane [335].…”

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confidence: 99%

“…Kinetics of ammonolysis of esters in nonaqueous media have been studied in [1,2]. There have been a number of works devoted to the effect of the structure of the RCO radical in ROX on the reactions of phenyl esters and derivatives of aliphatic carboxylic acids with various amines in dioxane [335].…”

mentioning

confidence: 99%

“…NH 2 CH(R)COO ! + I (1) The reaction was performed with a considerable excess of an a-amino acid (~10 !2 M) with respect to ester I (~10 !5 M). The concentration of the anionic form of the a-amino acid was created by adding a specified amount of NaOH into the reaction mixture.…”

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confidence: 99%

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Kinetics of N-acylation of α-amino acids with 4-nitrophenyl benzoate in aqueous 2-propanol

et al. 2004

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Kinetics of N-acylation of glycine, L-a-alanine, L-valine, L-leucine, and DL-isoleucine with 4-nitrophenyl benzoate in a water32-propanol solvent at various temperatures were studied. The activation energy, enthalpy, and entropy of the process were determined. Correlations of the N-acylation rate constants of the a-amino acids with the composition of the binary solvent at various temperatures were established, and the N-acylation rate constants of the a-amino acids in water were determined.Kinetics of ammonolysis of esters in nonaqueous media have been studied in [1,2]. There have been a number of works devoted to the effect of the structure of the RCO radical in ROX on the reactions of phenyl esters and derivatives of aliphatic carboxylic acids with various amines in dioxane [335]. Over the past years we have studied the kinetics of N-acylation of a-amino acids with benzoyl chloride in water3dioxane[638] and with carboxylic acid esters in water3 2-propanol, water32-methyl-2-propanol, and water3 acetonitrile [9, 10].The present work deals with the kinetics of N-acylation of glycine (Gly), L-a-alanine (L-Ala), L-valine (L-Val), L-leucine (L-Leu), and DL-isoleucine (DL-ILe) with 4-nitrophenyl benzoate (I) in water3 2-propanol.The N-acylation occurs at pH 839.5 by scheme (1).The reaction was performed with a considerable excess of an a-amino acid (~10 !2 M) with respect to ester I (~10 !5 M). The concentration of the anionic form of the a-amino acid was created by adding a specified amount of NaOH into the reaction mixture. We found that at a 1 : 431 : 10 ratio of the anionic (c a ) and zwitter ionic forms (c zi ) of the a-amino acid the rate of hydrolysis of ester I in water32-propanol can be neglected. The rate of reaction (1) follows the firstorder kinetic law (apparent rate constant k ap ). The second-order rate constant k ac of reaction (1) was calculated by Eq. (2). k a = k ap /c a .(2) Table 1 lists the acylation rate constants k ac of the amino acids studied with ester I in water32-propanol. By the ability for acylation, the a-amino acids can be arranged in the following order: Gly > L-Ala > L-Leu > DL-Ile > L-Val. As seen from Table 1, the N-acylation rate increases with increasing water fraction in the binary solvent, which is probably explained by formation of more reactive complexes II and III of the a-amino acids and ester I with the OH groups of solvent components R`OH (R`= H, i-Pr) via hydrogen bonding. The formation of H-complexes II and III should increase the negative charge of the a-amino acid nitrogen and the positive charge on the ester carbonyl carbon, which favors N3C bond formation and accelerates the reaction.

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Kinetics of N-acylation of α-amino acids with 4-nitrophenyl benzoate in aqueous 2-propanol

et al. 2004

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“…An alternate possibility involves the formation of charged intermediate species. [15][16][17] Reaction kinetics of low molecular weight compounds in solution have been used to predict the kinetics and mechanism of polymer reactions. 18 No kinetic investigation were carried out in this work to distinguish between these possibilities.…”

Section: Reaction Of Poly(e-co-ma-co-mah) With Oleylamine/ethanolaminementioning

confidence: 99%

Chemical modification of poly(ethylene‐co‐methyl acrylate‐co‐maleic anhydride) for cathodic electrodepositions

Percec

Howe

et al. 2011

J. Polym. Sci. A Polym. Chem.

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This study is concerned with the development of new polymers that could be deposited via cathodic electrocoating methods on metal surfaces. The synthetic strategy is based on the incorporation of cationic functionalities into commercial polymers. Polyalkyl acrylic or methacrylic ester copolymers were reacted with primary or secondary amines and aminoalkanols or their mixtures. Depending on the proportion of the acrylic or methacrylic ester in the starting material and the extent of the chemical modification, the resulting amide functionalized polymers are soluble or dispersible in water and could be used as aqueous dispersions for cathodic electrodepositions. Hindered amine catalysts, such as diazabicyclo[2.2.2]octane, accelerate the chemical transformation leading to higher level of functionalization. Among different amines screened, mixtures of oleylamine and ethanolamine proved to produce the best results. A poly(ethylene‐co‐methyl acrylate‐co‐maleic anhydride) [poly(E‐co‐MA‐co‐MAH)] was aminolyzed in solution with a mixture of 50/50 (mol % ratio) of oleylamine/ethanolamine and used to generate aqueous dispersions via phase inversion from methyl isobutyl ketone solutions. These dispersions exhibit particle sizes in the submicron range and zeta potential values indicating a good stability. They could be electrodeposited to give films of high elasticity according to the nanomechanical tests. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

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“…Therefore, the study and elucidation of their mechanism present a considerable interest. well understood(2) while a number of well established facts are known in aprotic solvents (3). It seems to be general in aprotic solvents that higher order terms in nucleophile appear in the kinetic eq~ation(~"'~) implying a general base catalysisi this catalytic effect can also be shown by unhindered tertiary a m i n e~(~) r the existence of tetrahedral intermediate is not definitely established but, if it exists, its collapse leading to products can ba considered as rate deter~uining'~).…”

Section: Transacylation Reactions Are Very Important In Chemistry Andmentioning

confidence: 99%

Mechanism of Ester Aminolysis in Aprotic Media and Specific Solvent Effects

Nagy

Reuliaux

Bertrand

et al. 1985

Bulletin des Soc Chimique

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The n-butylaminolysis of nitro-substituted 4'-nitrophenyl benzoates and cinnamates as well as of phenylacetates in aprotic solvents is governed by a kinetic law implying higher order terms in nucleophile. It is shown that the attacking nucleophile forms a n-a type molecular complex with the substrate before reaching the transition state in the subsequent kinetic step. This molecular complex is a true reaction intermediate as evidenced by the observed negative activation enthalpy. Othernlecules intervene as general base catalysts. Tertiary m i n e d also c a t a l y s 3 h e reaction. Their catalytic activity i s linearly related to their hydrogen bond forming ability and it is not a direct function of their proton basicity. By varying the nucleophile structure, an excellent BrOnsted relationship could be obtained for the first time in aprotic media, the 6 of which confirms that the catalytic collapse of tetrahedral intermediate is the rate determining step. The reaction of cinnamates turns out to be less sensitive to structural changes of th. substrate than is the reaction of benzoates as shown by the corresponding Hammetovalues. The electronic effects of 2-nitro groups are strongly solvent dependent. Once more, it is established that &enever specific solvent effects (n-donor or ndonor ability) are present, they dominate the overall effect. A general reaction mechanism is proposed which not only explains the various roles played by the nucleophile but also accounts successfully for the great variety of kinetic schemes observed in aprotic media. Transacylation reactions are very important in chemistry and biology.Therefore, the study and elucidation of their mechanism present a considerable interest. well understood(2) while a number of well established facts are known in aprotic solvents(3). It seems to be general in aprotic solvents that higher order terms in nucleophile appear in the kinetic eq~ation(~"'~) implying a general base catalysisi this catalytic effect can also be shown by unhindered tertiary a m i n e~(~) r the existence of tetrahedral intermediate is not definitely established but, if it exists, its collapse leading to products can ba considered as rate deter~uining'~).In the present paper, we attempt to elucidate further the mechanism of ester aminolysis reactions. We also show the influence of structural and solvent effects on this mechanism.A series of nitro-substituted benzoates, cinnamateb and acetates has been submitted to n-butylaminolysis in various aprotic solvents (Table 1). The solvents have been chosen in such a way as to represent both general (polarity, The mechanism of ester aminolysis reactions in aqueous media is fairly -1055 -

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Rate-determining collapse of a tetrahedral intermediate in ester aminolyses in aprotic solvents

Cited by 14 publications

References 13 publications

Kinetics of N-acylation of α-amino acids with 4-nitrophenyl benzoate in aqueous 2-propanol

Kinetics of N-acylation of α-amino acids with 4-nitrophenyl benzoate in aqueous 2-propanol

Chemical modification of poly(ethylene‐co‐methyl acrylate‐co‐maleic anhydride) for cathodic electrodepositions

Mechanism of Ester Aminolysis in Aprotic Media and Specific Solvent Effects

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